It is proposed to continue the study of the sequential analysis of the development of liver cancer using a combined biochemical-biological approach. Emphasis is to be given to the further refinement of a model that may allow the sequential analysis and to be the exploitation of the model to analyze the process of initiation and promotion. It is proposed to explore new avenues by which the resistant hepatocytes induced, by an initiating dose of a carcinogen such as MNU, DEN or DMH, can be selected or promoted for rapid growth. Methotrexate and choline deficiency are to be used. In addition, attempts will be made to influence in a major way the two known options available to the hyperplastic nodules -remodeling and persistence. Bromodeoxyuridine and azacytidine, compounds known to influence differentiation, are also to be used. Also, the role of cell proliferation in the initiation process is to be analyzed. First emphasis will be placed on determining whether DNA synthesis is or is not required to initiate liver cancer formation with chemicals. In addition, the study of markers for preneoplastic hepatocytes will be continued. Nuclear and nucleolar and membrane markers are to be explored as well as HCG and PN antigen.